Liquid crystal display apparatus and method and apparatus for driving same

• US 5,438,342 A
• Filed: 05/15/1992
• Issued: 08/01/1995
• Est. Priority Date: 05/15/1991
• Status: Expired due to Term

• Current Assignee: AU Optronics Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Yamaguchi, Hidefumi
• Primary Examiner(s): Brier, Jeffery
• Assistant Examiner(s): Au, A.
• Application Number:
  US07/883,090
• Time in Patent Office: 1,173 Days
• Field of Search: 340/784, 340/805, 340/811, 345/58, 345/79, 345/96, 345/54, 345/98, 345/99, 345/100, 345/87
• US Class Current: 345/58
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A method and an apparatus for driving a liquid crystal display, in which flicker and cross talk are removed for arbitrary display patterns. The liquid crystal display has a plurality of scan lines, a plurality of data lines, and a plurality of pixels arranged in a matrix at the intersections of the scan and the data lines. The polarity of data signals outputted to the data lines is inverted for each occurrence of a pixel to be placed into a predetermined state. The predetermined state may be a dark state or a bright state of a binary display, or one of several levels of a display having more than two gray scale levels.

Claims

1. A method for driving a liquid crystal display apparatus that includes a plurality of scan lines, a plurality of data lines, a plurality of pixels arranged in a matrix at the intersections of said scan lines and said data lines and a driver for driving the data lines with a data signal representing successive pixel states and at a polarity determined by a polarity signal, said polarity signal having a polarity value representing one of two different polarity values for each of said successive pixel states, wherein the improvement comprises the step of:

changing said polarity value of said polarity signal for each occurrence of a predetermined pixel state.

2. The method of claim 1, wherein said predetermined pixel state is representative of a dark state of a pixel in a normally white mode of operation.

3. The method of claim 2, wherein each pixel has only two states and said dark state is one of said two states.

4. The method of claim 2, wherein said predetermined pixel state is representative of one of several states of a gray scale of said liquid crystal display apparatus.

5. The method of claim 1, wherein said predetermined pixel state is representative of a bright state of a pixel in a normally black mode of operation.

6. The method of claim 5, wherein each pixel has only two states and said bright state is one of said two states.

7. The method of claim 5, wherein said predetermined pixel state is representative of one of several states of a gray scale of said liquid crystal display apparatus.

8. A liquid crystal display apparatus comprising:

a plurality of scan lines;

a plurality of data lines;

a plurality of pixels arranged in a matrix at intersections of said scan lines and said data lines;

a data driver for receiving a digital data signal representing successive pixel states each by a predetermined number of bits and for outputting a data signal to said data lines to drive said pixels, said data driver providing data signals of alternating polarity to said data lines in accordance with a polarity signal, said polarity signal having a polarity value representing one of two different polarity states for each of said successive pixel states; and

means for creating said polarity signal so as to change said polarity value each time a predetermined one of said number of bits representing a successive pixel state has a predetermined value,

whereby the polarity of the data signals outputted to said data lines is inverted for each occurrence of a pixel state in which said predetermined one of said number of bits representing said pixel state has said predetermined value.

9. The liquid crystal display apparatus according to claim 8, wherein said pixels are bright when not driven and wherein said predetermined value corresponds to a dark pixel state.

10. The liquid crystal display apparatus according to claim 8, wherein said pixels are dark when not driven and wherein said predetermined value corresponds to a bright pixel state.

11. The liquid crystal display apparatus according to claim 8, wherein said predetermined number of bits is at least two.

12. The liquid crystal display of claim 8 wherein said means for creating said polarity signal comprises:

a first logic means having a clock input and a data output,

a second logic means having a clock input, a preset input, a data input and a data output,

means for providing a start frame signal to the clock input of said first logic means and to the preset input of said second logic means,

means for providing a clock signal to said clock input of said second logic means,

means for providing an input signal to said data input of said second logic means, and

a third logic means having first and second inputs and an output, said data output of said first logic means being connected to said first input of said third logic means and said data output of said second logic means being connected to said second input of said third logic means,

said output of said third logic means corresponding to an exclusive OR condition of said first input and said second input of said third logic means.

13. The liquid crystal display of claim 12 wherein the first logic means and the second logic means are flip-flops.

14. The liquid crystal display of claim 12 wherein said means for providing an input signal provides a most significant bit of said digital data signal.

15. The liquid crystal apparatus according to claim 8, wherein said predetermined number of bits is one.

16. A liquid crystal display apparatus comprising:

a plurality of scan lines;

a plurality of data lines;

a plurality of pixels arranged in a matrix at intersections of said scan lines and said data lines;

a data driver for receiving a digital signal representing successive pixel states each by a predetermined number of bits and for outputting a data signal to said data lines to drive said pixels;

driving means for driving the liquid crystal display apparatus with alternating current wherein the polarity of said data signal outputted to said data lines is controlled in accordance with a polarity signal, said polarity signal having a polarity value representing one of two different polarity states for each of said successive pixel states; and

means for creating said polarity signal so as to change said polarity value each time a predetermined one of said number of bits representing a successive pixel state has a predetermined value.

17. The liquid crystal display of claim 16 wherein said means for creating said polarity signal comprises:

a first logic means having a clock input and a data output,

a second logic means having a clock input, a preset input, a data input and a data output,

means for providing a start frame signal to the clock input of said first logic means and to the preset input of said second logic means,

means for providing a clock signal to said clock input of said second logic means,

means for providing an input signal to said data input of said second logic means, and

a third logic means having first and second inputs and an output, said data output of said first logic means being connected to said first input of said third logic means and said data output of said second logic means being connected to said second input of said third logic means,

said output of said third logic means corresponding to an exclusive OR condition of said first input and said second input of said third logic means.

18. The liquid crystal display of claim 17 wherein the first logic means and the second logic means are flip-flops.

19. The liquid crystal display of claim 17 wherein said means for providing an input signal provides a most significant bit of said digital data signal.